Stents are often employed in a variety of patient treatment and diagnostic procedures. They are usually implanted within blood vessels, biliary ducts and other body lumens to maintain their passageways. For example, a radially self-expanding stent can be deployed in an artery following a percutaneous transluminal coronary angioplasty (PTCA) procedure or a percutaneous transluminal angioplasty (PTA) procedure. The stents resists a tendency in the vessel to close, thus countering acute reclosure and plaque restenosis. A variety of stents, and methods for delivering them, are disclosed in the prior art.
One method frequently described for delivering a stent to a desired intraluminal location includes mounting and crimping the expandable stent on the expandable member of a catheter, such as a balloon, which is provided on its distal end. The catheter is advanced to the desired location within the patient's body lumen and the balloon is subsequently inflated to expand the stent into a permanent expanded condition and then the balloon is deflated and the balloon and catheter removed from the body lumen leaving the stent permanently implanted.
Another method frequently described for delivering a stent to a desired intraluminal location includes mounting the stent on the distal end of a catheter, where the stent is a self-expanding stent formed from self-expanding stainless steel, or shape memory alloys such as nickel titanium (NiTi). The self-expanding stents are implanted by advancing the catheter to the desired location within the patient's body lumen, withdrawing a sheath so that the stent can self-expand into the body lumen, and then withdrawing the catheter and sheath leaving the stent implanted.
Regardless of the stent type, its deployment frequently involves guiding a catheter or other delivery appliance through convoluted paths defined by arteries or other body passages. A well known technique for guiding the delivery catheter includes initially positioning a guidewire along the desired path, with the distal end of the guidewire near the treatment site and a proximal portion of the guidewire remaining outside of the body. The delivery catheter has a lumen that runs throughout its length. The distal end of the delivery catheter is threaded over the proximal end portion of the previously positioned guidewire so that it may be advanced distally over the guidewire, ultimately to the treatment site for stent deployment.
Procedures that employ guidewires often require exchanging of treatment appliances. This exchange of catheters usually requires that the proximal portion of the guidewire be protruding from the patient's body and be longer than any catheter involved in the procedure. Because of the difficulty created in maneuvering the guidewire and catheters and the substantial frictional force generated by the guidewire and catheter interaction, rapid exchange methods have been developed. These rapid exchange methods are well known in the art.
Attempts have also been made to deliver stents on guidewires to reduce the overall profile of the delivery system.
One of the problems encountered in using these prior art stents is the inability to tightly crimp the stent, either on the balloon portion of the catheter, or onto its distal end, or on a delivery guidewire. However, because it is still desirable that the stent have a small diameter for delivery purposes, yet be able to expand to various diameters to hold open the lumen after implanting, better delivery devices and methods are needed. Such delivery devices could also be utilized to deliver other vascular implants.